Unity is better for 3d. All I need is a physics engine.

I've decided to use http://www.jbox2d.org/ as my physics engine. I suggest you play with this: http://gwtbox2d.appspot.com/

This engine was used in Angry Birds and others, It is free and open source (zlib license). I've decided to stick with java because it is cross platform by default and a port to android wouldn't be too hard.